The present invention relates to an apparatus for transporting a tape (for example, magnetic tape) from a reel directly to another reel, and more particularly to a method and apparatus for controlling tape transportation suitable for high speed and high precision tape transportation.
In a prior art apparatus such as that disclosed in U.S. Pat. No. 4,125,881, a current command to correct a tape velocity and a current command to correct a tape tension are separately issued to a reel drive system. However, a relationship between those two current commands is not clear but they are determined separately.
A direct reel-to-reel tape transportation apparatus without vacuum buffers in which respective reels are driven by two motors and the rotations of the motors are detected by tachometers to control a tape velocity spanned and transported between the reels to a predetermined velocity is also disclosed in U.S. Pat. No. 4,351,166 and U.S. Pat. No. 4,525,654. In those U.S. Patents, however, the relationship between the current commands for the motors to drive the reels is not clearly defined.
In the techniques of the above references, attention is not paid to a tape velocity and a tension in a vicinity of a magnetic head, and they have a problem in precision. For example, a measurement of a peripheral velocity of one reel is regarded as a tape velocity in the vicinity of the magnetic head. Further, since the current command to modify the tape tension is not always determined in accordance with a physical constant of the reel drive system, it is uncertain and imports unnecessary external force to the tape velocity.